1. Field of the Invention
The present invention relates to a paper-feeding apparatus of an image forming apparatus, i.e., an office machine such as a copier, a printer or a fax machine, and more particularly, to a paper-feeding apparatus of an image forming apparatus having a part to vary a paper-entering angle to prevent a sheet pickup problem. Examples of the pickup problem are multi sheet feed or a sheet feed failure. These problems may be overcome by varying the angle of the leading end of a sheet touching the paper separating member. Specifically, the problems may be overcome by varying the angle of the leading end of a sheet entering the paper separating member according to the thickness or stiffness of the paper being fed.
2. Description of the Related Art
An image forming apparatus, i.e., an office machine, such as a printer or a fax machine, generally includes a paper-feeding apparatus feeding sheets of paper to an image forming unit.
As shown in FIG. 1, such a paper-feeding apparatus 10 includes a frame 11 forming a stacker or a tray to stack paper, a pickup unit 30 disposed at the lower side of the frame 11 (right hand side of FIG. 1) to rotate in association with a power transferring gear train (not shown) connected with a pickup roller driving motor (not shown) and to pick up sheets of paper stacked in the frame 11. The apparatus 10 also includes a paper separating assembly (not shown) including a plurality of paper separating members 40 (only one is shown) integrally or separately disposed to the frame 11 at the lower side of the frame 11 to separate and feed one sheet of paper at a time while supporting the sheet of paper to enter at a predetermined angle. A rigid bottom portion 20 of the frame 11 supports the paper separating members 40.
The pickup unit 30 includes a pickup roller assembly 33 including a pickup shaft 31 connected to the power transferring gear train, a first gear (not shown) formed around the pickup shaft 31, and first and second idle gears (not shown) pivotably disposed around first and second idle shafts 37, 38 to move in association with the first gear, and a pickup roller gear (not shown) connected to the second idle gear. The pickup unit 30 further includes a unidirectional power transfer unit (not shown) such as a spring clutch to transfer rotational power only in the paper pickup direction between the pickup roller gear and the pickup roller 34, and a link member 36 with one end connected with the pickup roller 34 to support the pickup roller 34 to be in contact with paper, and the other end pivotably supported by a supporting shaft 35.
Hereinafter, the operation of the conventional paper-feeding apparatus 10 having the above structure will be described.
When a paper feed mode is selected, the pickup shaft 31 rotates in the pickup direction, for example, clockwise, by the power transferring gear train connected to the pickup roller driving motor, and accordingly the pickup roller 34 rotates counter-clockwise in association with the first gear, the first and second idle gears and the pickup roller gear.
As a result, a sheet of paper in contact with the pickup roller 34 is picked up and fed as the pickup roller 34 rotates counter-clockwise.
The paper picked up by the pickup roller 34 is separated sheet by sheet while being supported at a predetermined angle by the paper separating member 40 of the paper separating assembly and then conveyed to an image forming unit (not shown).
After that, when the paper activates a paper sensor (not shown), a control unit (not shown) stops the pickup roller driving motor and starts a convey roller driving motor (not shown), or transfers the driving force of the pickup roller driving motor to a convey roller driving unit (not shown), thereby driving a convey roller (not shown) through a power connection/blocking device such as a swing gear (not shown) in order to stop the pickup roller 34 and drive the convey roller (not shown) to convey the paper.
As a result, the paper is continuously conveyed to the image forming unit by the convey roller. The pickup roller 34 receiving counter-clockwise rotational force from the paper idly rotates without transferring rotational force to the pickup roller gear due to the unidirectional power transfer unit of the pickup roller assembly 33.
However, in order to support the paper to enter at the predetermined angle, the conventional paper-feeding apparatus 10 has the paper separating member 40 disposed to adjust the paper entering angle based on a type of paper having a commonly used thickness.
Accordingly, if the paper being fed to the paper-feeding apparatus 10 is thicker than the common paper, for example, photo paper, the paper-entering angle of the paper separating member 40 becomes not suitable for the photo paper.
If the paper-entering angle of the paper separating member 40 is not suitable for the photo paper, a sheet pickup problem such as multi sheet feed or a sheet feed failure may occur.